A preferred liquor for use in preparation of pulp and extraction of lignin from wood has been described in U.S. Pat. Nos. 3,442,753 and 3,522,230 to Burkart, both of which are incorporated herein by reference in their entirety.
U.S. Pat. No. 4,826,566 discloses an improved method for treating ligno-cellulosic material to remove lignin and to obtain cellulose and other valuable products from paper, chips or other forms of cellulosic materials.